1. Field of the Invention
The present invention relates to a reproduction system including, for example, a reproduction apparatus (disc drive) capable of performing a reproduction operation with respect to a disc recording medium, and a host device (e.g., computer having a disc driver function) connected to the reproduction apparatus so as to direct it to perform reproduction. More the present invention also relates to a reproduction method thereof.
2. Description of the Related Art
Compact discs (CDs) such as optical-disc recording media have come into wide use, and CD-system discs are used in various fields. In particular, compact disc read only memories (CD-ROMs), compact disc recordables (CD-Rs), and so forth, are widely used for computers.
In addition, discs called "digital versatile discs" or "digital video discs" (DVDs) suitable for multimedia use have been developed. The DVDs are adapted for various types of data such as video data, audio data and computer data. Although the DVDs have a size (diameter of 12 cm) equal to that of a CD, they have a storage capacity which is remarkably increased by using a smaller-pitch recording-track formation, data compression techniques.
The DVDs include types such as digital versatile disc read only memories (DVD-ROMs) used only for reproduction, digital versatile disc rewritables (DVD-Rs) capable of being rewritten once, and digital versatile disc random access memories (DVD-RAMs).
It has been proposed that the DVD-RAM media use a replacement processing for defect management since they have a random access function.
In other words, when a defective region is found by checking a disc while the disc is being formatted or used, the defective region is assigned to another region. Subsequently, information on the defective region and information on the assignment region are recorded as defect management information (defect map) in a particular area on the disc.
When an actual reproduction request is generated, a logical address as to the request is transformed to the physical address corresponding to a real address on the disc. If the logical address includes a portion corresponding to the defective region managed with the defect management information, an address where an actual reading operation is performed must be generated by executing the step of transforming only the address of the defective portion to the address of a replacement region.
Conversely, the DVD-ROM media do not need defect management including such a replacement process.
The structure of a DVD drive (DVD reproduction apparatus) will be described. If the reproduction apparatus is adapted for only a DVD-ROM, the reproduction apparatus needs no defect management function. Accordingly, when a reproduction request is sent from the host computer, all that is required is the function of transforming to a physical address a logical address as reproduction-position information sent from the host computer connected to the reproduction apparatus. In general, logical addresses are such that the beginning of the user area of a disc is used as the start (address zero). Physical addresses are addresses, numbered from the start, including a control information area formed before the user area. Thus, transforming the logical address to the physical address simply needs offset addition which adds to the logical address an address value before the user area, which eliminates the need for using relatively large firmware for providing the function of transforming the logical address to the physical address. Accordingly, a reproduction apparatus adapted for only a DVD-ROM can be very inexpensively provided.
However, a reproduction apparatus adapted for only a DVD-RAM must have the structure of a disc reproduction apparatus 91 shown in FIG. 1.
FIG. 1 uses reproduction functional blocks to show the disc reproduction apparatus 91 and a host computer 92. The host computer 92 is loaded with software as a device driver 96 functioning under an operating system (hereinafter referred to as an "OS") 97 in order to be adapted for the disc reproduction apparatus 91. The device driver 96 includes a file system function 96a for reading and holding file management information from a disc loaded into the disc reproduction apparatus 91, and a driver function 96b which functions to execute the reading of file data requested by the OS 97 from file data managed by the file system function 96a.
The disc reproduction apparatus 91 includes a driving unit 93 (for enabling the actual reproduction of data from the disc) composed of, e.g., an optical head, a servo mechanism and a decoding circuit, and a controller 94 for causing the disc driving unit 93 to execute a necessary reproducing operation based on a request from the host computer 92.
The disc reproduction apparatus 91 and the host computer 92 are connected to each other by a small computer system interface (SCSI) or AT attachment packet interface (ATAPI) communication.
According to the above-described reproduction system including the host computer 92 and the disc reproduction apparatus 91, when a read request to a certain data file is generated from the OS 97, the disc driver 96 transmits to the disc reproduction apparatus 91 a read command and positional information for executing a reading operation. The positional information consists of, for example, the start address of a range to be read and a data file length (data length). The start address to be transmitted is a logical address based on the data file management of the disc by the host computer 92.
The controller 94 of the disc reproduction apparatus 91 receives the read command, the address and the data length (as the positional information) transmitted from the host computer 92, and causes the disc driving unit 93 to execute a reading operation in accordance with the transmitted command and information. In the disc driving unit 93, an actual access operation is performed based on a physical address. Accordingly, the transmitted logical-address and data-length information needs to be transformed to physical-address and length information.
For the DVD-ROM medium, by simply adding an offset value to a logical address, a physical address as the sum can be obtained. For this operation, an offset adding function 94a is provided in the controller 94.
Conversely, for DVD-RAM medium, it is required to respond to the defect management condition. Accordingly, in the controller 94 are provided a defect table function 94b for holding a table created based on defect management information read from the disc and replacement information included therein, namely, a defect table created to facilitate address transformation in accordance with replacement information, and an address transformation function 94c for performing address transformation in accordance with the created defect table.
By providing these functions 94a and 94b, address transformation can be performed, if necessary, based on the replacement information in accordance with a defect such as a scratch, and a physical address where data included in the data file to be read is actually recorded and the data length can be generated. The controller 94 commands the disc driving unit 93 to perform a reproducing operation at the location represented by the physical address and the data length.
This executes the reproduction of the data file requested by the disc driving unit 93, and the reproduced data file is transmitted to the host computer 92.
As described above, the reproduction apparatus adapted for the DVD-RAM must have the defect table function 94b and the address transformation function 94c for executing defect management. In order for that the reproduction apparatus adapted for the DVD-RAM to hold defect management information, if the maximum number of defects is d and address data is a (e.g., approximately 7 to 8) bytes in length, a storage region having d.times.a bytes is necessary. If the maximum number of defects=2000, a storage region having 14 to 16 kilobytes is necessary.
The reproduction apparatus adapted for only the DVD-ROM in which such a storage region is unnecessary needs a storage capacity of several kilobytes, and for which the built-in RAM of the CPU of the controller 94 is normally used. However, in order for the reproduction apparatus adapted for only the DVD-ROM to may be adapted for the DVD-RAM, additional storage of 14 to 16 kilobytes is necessary.
In addition, using the stored defect management information to create the defect table and using the defect table to perform actual address transformation requires firmware having a relatively large size. In general, the size of the firmware is several kilobytes.
Additionally providing the storage capacity and the firmware disadvantageously brings about an increase in disc reproduction apparatus size and cost.